The present invention relates to a screen printer for printing paste such as cream solder, electrically conductive paste, etc. to a substrate.
In a mounting process of an electronic part, screen printing is used as a method for printing paste such as cream solder, electrically conductive paste, etc. onto the substrate. In this method, a mask plate having a pattern hole arranged in accordance with a printing object part is abutted on the substrate and a squeegee is slid by supplying the paste onto the mask plate so that the paste is printed onto the substrate through the pattern hole.
In the screen printing, it is necessary to closely attach the substrate to the mask plate, and correctly hold the position of the substrate so as not to cause a horizontal position shift. Therefore, a lower receiving portion abutted on the lower face of the substrate and supporting the substrate, and a clamp mechanism for nipping a side end portion of the substrate from both sides thereof and holding the position of the substrate are arranged in a substrate holding portion for holding the substrate.
There are many cases in which the carried-in substrate is generally flexed, warped and deformed in the thickness direction. Therefore, a screen printer in which a mechanism for correcting the flexure by pressing the substrate held to the substrate holding portion from the upper side is arranged in a place except for a printing position is known for the purpose of correcting the warp of the substrate in the clamping in the substrate holding portion (e.g., see Japanese Patent Publication 2001-38876).
However, in the above conventional screen printer, an equipment occupying area and equipment cost are increased by separately arranging the mechanism for correcting the flexure, and disadvantages of clamp dislocation explained below are easily caused. Namely, in the above screen printer, it is necessary to move the substrate holding position until the printing position after the substrate is clamped. However, in the case of the substrate of a kind tending to be strongly warped, the disadvantage that the substrate is dislocated from the clamp state during this movement is caused. Thus, in the conventional screen printer, a problem exists in that it is difficult to reliably hold the clamp state by correcting the warp deformation of the substrate by a simple and cheap mechanism.